Singlet-to-Triplet Conversion in Gas-Phase Naphthalene, Phenanthrene, and Anthracene

Abstract

A new method is presented for studying the radiationless process of singlet‐to‐triplet conversion in systems demonstrating delayed fluorescence via triplet—triplet annihilation. The usefulness of the technique was illustrated through application to the gas‐phase emission of anthracene, naphthalene, and phenanthrene. The ratio of the first‐order conversion constant k_ST to the singlet decay constant k in the pressure regions examined was 0.3 for anthracene (1–3 mm) and 0.2 for naphthalene (10–50 mm). For phenanthrene, k_ST/k increased from 0.3 to about 0.9 with increasing phenanthrene pressure from 10 to 50 mm. In all cases addition of N₂ showed no effect.